1. Field of the Invention.
This invention relates generally to electrostatic transducers, and particularly relates to a driver circuit therefor.
2. Description of the Prior Art.
The present invention may be considered to be an improvement over the applicant's prior U.S. Pat. No. 4,006,713.
Prior art driver circuits for electrostatic tranducers are genreally arranged to drive the stators of the transducer while a direct current voltage is applied between the diaphragm and both stator plates. The diaphragm is supplied with a voltage of one polarity and both stator plates with the other. However, generally the driver circuits are arranged so that the audio signal is also fed back onto the stator plates. This in turn means that the voltages applied to the stator plates vary together with the audio signal. Because the stator plates are fixed and rigid, the portion of the audio signal applied across the stator plates represents a loss of energy and, hence, decreased efficiency.
Furthermore, due to the type of driver circuits known in the past, it has not been possible to apply a DC bias voltage which was unmodulated across the stator plates which is as high as, or higher than the peak audio voltage, It will be evident that the higher the DC bias voltage between the stator plates is, the higher is the resulting efficiency. Also, by having a steady biasing field, the response of the transducer is more linear with respect to the audio modulation impressed on the diaphragm.
It is accordingly an object of the present invention to provide a driver circuit for an electrostatic transducer which overcomes the disadvantages of the prior art.
Another object of the present invention is to provide a driver circuit which makes it possible to create a DC bias field between the stator plates which may be as high as, or higher than the peak audio voltage.
A further object of the present invention is to provide a driver circuit of the type discussed which makes it possible to apply the alternating audio signal onto the diaphragm and to omit the variations of the audio signal on the respective driver plates.
Still another object of the present invention is to supply the required electrostatic field between the stator plates by electrets of the opposite polarity on respective stator plates.
Still a further object of the invention is to eliminate resonance between the transducer and its driving source.
The novel features that are considered characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description when read in connection with the accompanying drawing.